JP2622582B2 - Method for manufacturing low-temperature fired substrate - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for producing a multilayer wiring board having a low firing temperature and capable of using silver as a conductor. More specifically, a mixed powder of mullite and lead borosilicate glass is cooled to a low temperature. The present invention relates to a method for manufacturing a substrate to be fired.

[Conventional technology]

Conventionally, as a ceramic multilayer substrate, mullite ceramics have a smaller dielectric constant than alumina ceramics,
Although useful because of its low coefficient of thermal expansion, it is difficult to obtain high-purity mullite, and alumina-based ceramic substrates occupy the majority.

However, recently, since high-purity mullite has been produced, ceramic sintered bodies have been produced from mullite and glass powder containing aluminum silicate or aluminum magnesium silicate as a main component (Japanese Unexamined Patent Publication No. No. 57-115895).

[Problems to be solved by the invention]

However, the above mullite ceramic sintered body is 1400-16
Since a high sintering temperature of 00 ° C. is required, a special sintering furnace is required, and sintering can only be performed in a reducing atmosphere.

Therefore, glass powder mixed with mullite powder has been studied in various ways, and it has been proposed to use borosilicate glass. However, although this has a small dielectric constant of 4.8 degrees, although the firing temperature has been improved, it must be used at about 1000 degrees Celsius. The problem of necessitating firing in a neutral atmosphere and requiring a special firing furnace has not been solved.

Therefore, the present inventors have repeatedly studied to obtain mullite ceramics that can be fired in the air at a firing temperature of 950 ° C. or less where silver can be used as a conductor, and use lead borosilicate glass as a glass powder to be mixed with mullite powder Thus, the object has been achieved, and the invention described below has been achieved.

[Means for solving the problem]

That is, the present invention relates to 40 to 70 wt% of PbO, _{20 to} 50 wt% of SiO2,
Glass powder containing _{2 to} 15 wt% of ₂ O _{3 and 1 to} 10 wt% of Al ₂ O ₃
A gist of the present invention is a method for producing a low-temperature fired substrate, wherein a mixed powder comprising 30 to 70 wt% and mullite powder 70 to 30 wt% is formed into a sheet and fired at 850 to 950 ° C.

The lead borosilicate glass used in the present invention is PbO40
_{~70wt%, SiO 2 20~50wt%,} B 2 O 3 5~15wt%, Al 2 O 3 1~1
0 wt% is a component. To make this glass, dry mixing of lead oxide (Pb ₃ O ₄ ), amorphous silica (SiO ₂ ), boron oxide (B ₂ O ₃ ), and aluminum oxide (Al ₂ O ₃ ) in a ball mill Then, after melting at 1400 ° C. in an electric furnace, the melt is put into water and rapidly cooled. The obtained glass lump is wet-pulverized by a vibration mill (made of medium ZrO ₂ ) and dried to obtain a glass powder. The average particle size of the glass powder is 1.0 μm, the maximum particle size is 4.7 μm, and the softening temperature is about 600 ° C.

On the other hand, the mullite powder was prepared by mixing aluminum hydroxide and amorphous silica in such a manner that the proportion of Al ₂ O ₃ was 71.8 wt% and the remainder was SiO ₂ , wet-mixed, dried and calcined at 1600 ° C. for 1 hour. Then, the obtained calcined product is pulverized with a vibration mill (made of medium Mullite) to obtain. The average particle size of the mullite powder was 0.2 μm, and the maximum particle size was 7 μm.

As an example of the method for producing the substrate of the present invention, a blend ratio of lead borosilicate glass powder of 70 to 30% to mullite powder 30 to 70% by weight, polyvinyl butyral (PVB) as a binder, and dibutyl phthalate as a plasticizer (DB
P) and ethanol as a solvent are added to form a slurry. This slurry was prepared to a thickness of 0.12 by the doctor blade method.
A sheet of mm is produced, several sheets of this sheet are laminated, surface pressed, debindered, and fired at 850 to 950 ° C.

In the present invention, firing can be performed in the air using a general firing furnace, and no special equipment or device such as a reducing atmosphere is required.

〔Example〕

Examples 1 to 15 and Comparative Examples 1 to 11 Oxide salts, amorphous silica, boron oxide, and aluminum oxide were produced in the proportions shown in Table 1 on mullite powder obtained from the above-described aluminum hydroxide and amorphous silica. The resulting lead borosilicate was blended in the ratio shown in Table 1, and PVBB, DBP and ethanol were added to form a slurry, and a sheet having a thickness of 0.12 mm was produced from the slurry by a doctor blade method.

Ten sheets obtained were laminated, and the laminated body was heated at 80 ° C. for 10 hours.
The face was pressed for minutes. Next, the binder was removed at 350 ° C. for 60 minutes, followed by baking at 850 to 950 ° C. for 15 minutes. 10x fired body
After processing to 10 × 1 mm, an Ag electrode was applied and baked at 700 ° C. The dielectric constant and the dielectric loss of this sample were measured at 25 ° C. at a frequency of 1 MHz. The results are shown in Table 1.

Example 16 Using the sheet prepared in Example 1, an eight-layer substrate with internal wiring as shown in FIG. 1 was prepared (sintering temperature: 900 ° C.), and the conduction between the upper electrode and the lower electrode was examined. There was no good substrate.

The coefficient of thermal expansion of this substrate measured at room temperature to 500 ° C. was 4.1 × 10 ⁻⁶ / ° C.

〔The invention's effect〕

According to the present invention, the use of lead borosilicate glass for the glass as the mullite ceramic makes it possible to fire at a low temperature, and there is no need to use copper for the conductor, so that firing does not have to be performed in a reducing atmosphere. No special firing furnace is required. Further, a good multilayer wiring board having a small dielectric constant and a small coefficient of thermal expansion can be manufactured.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an example of an eight-layer board with internal wiring according to the sixteenth embodiment. DESCRIPTION OF SYMBOLS 1 ... Through-hole conductor (Ag) 2 ... Internal conductor (Ag) 3 ... Upper external electrode 3 '... Lower external electrode 4 ... Insulator sheet

Claims (1)

(57) [Claims] 1. PbO 40 to 70 wt%, SiO _{2 20 to} 50 wt%, B ₂ O ₃ 5 to
15 wt%, glass powder 30-70 to Al ₂ O ₃ 1~10wt% of component
A method for producing a low-temperature fired substrate, comprising forming a mixed powder comprising wt% and 70 to 30 wt% of mullite powder into a sheet and firing at 850 to 950 ° C.